The 2,3-diphosphoglycerate- independent phosphoglycerate mutase (iPGM) catalyzes the interconversion of 3-phosphoglycerate (3PGA) and 2-phosphoglycerate (2PGA). They are the predominant PGM in plants and some other bacteria, including endospore forming Gram-positive bacteria and their close relatives. The two steps catalysis is a phosphatase reaction removing the phosphate from 2- or 3-phosphoglycerate, generating an enzyme-bound phosphoserine intermediate, followed by a phosphotransferase reaction as the phosphate is transferred from the enzyme back to the glycerate moiety. The iPGM exists as a dimer, each monomer binding 2 magnesium atoms, which are essential for enzymatic activity.
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